The idea is nothing new. Not at all. For some time now, tech followers have dreamed about Gates’ return to the fledgling software superpower – a la Steve Jobs’ return to near-bankrupt Apple.

Block, on his personal blog, today mused:

There’s taste, though, and there’s cunning — and it was Bill’s killer instinct that made Microsoft the undisputed winner of the first wave of personal computing. And with each passing quarter, it’s becoming increasingly clear that in matters of both taste and cunning, Steve Ballmer has neither. Paging Dr. Gates: you’re needed in the ER. …

I’m not saying Bill’s going to leave his new gig as the world’s greatest living philanthropist with aplomb, but the multi-billion dollar wheels at The Gates Foundation have been set in motion — and lest we all forget, the Foundation’s endowment is tied directly to Microsoft’s long-term success. It may just happen that Bill can help the Foundation more by securing Microsoft’s future.

How long can Ballmer’s bluster substitute for real leadership, and how much dumb money can Microsoft throw at its “strategy?” Former GM at Microsoft (and now SVP at Google) Vic Gundotra recently said of Microsoft’s partnership with Nokia, “Two turkeys don’t make an eagle.” And he’s absolutely right, no amount of Dangers and Skypes and Nokias and RIMs and any other outsized, bloated multi-billion dollar acquisitions can make up for vision at the helm. Bill doesn’t have a spotless track record either, but he’s a master at making calculated gambles on people and projects that break new ground and define the future.

The problem is, Gates has made it pretty clear he has no interest in returning to day-to-day responsibilities at Microsoft. He’s still chairmain, and seems to be satisfied with dealing only with the bigger-than-big picture. But CEO?

Of course, the billion-dollar question is, “Well, if not Gates, who else could lead Microsoft?”

In the comments section, a GDGT reader suggests Joe Belfiore, the charismatic corporate vice president for Windows Phone Program Management who often gives compelling presentations at tech conferences. Another commenter asked about Steve Wozniak, who cofounded Apple along with Steve Jobs and continues to be outspoken about new technology.